Flap-type abrasive wheel



.Dec. 22,1970 3,548,551

FLAP-TYPE ABRASIVE WHEEL Filed June 2, 1967 3 Sheets-Sheet l -A m Anne/var; I

D86. 22, 1970 BLOCK 3,548,551

FLAP-TYPE ABRASIVE WHEEL Filed June' 2, 1967 I 3 Sheets-Sheet 2 IIVMEIVTOA Arramverg Dec. 22, 1970 A. BLOCK 3,543,551

I FL APTYPE ABRASIVE WHEEL Filed June 2, 1967 '3 Sheets-Sheet S ike/1554 4rme/ven f United States Patent O 3,548,551 FLAP-TYPE ABRASIVE WHEEL Aleck Block, Los Angeles, Calif., assignor, by mesne assignments, to Merit Abrasive Products, Inc., Los Angeles, Calif., a corporation of California Filed June 2, 1967, Ser. No. 643,101 Int. Cl. B24d 13/14 U.S. Cl. 51--337 7 Claims ABSTRACT OF THE DISCLOSURE Packs of abrasive leaves are mounted on a rotary hub with enlargements at the base ends of the packs in removable interlocking engagement with corresponding longitudinal slots in the periphery of the hub. Various improvements taught by the invention relate to: provisions for replacement of portions of the slots; compacting and solidifying expensive base portions of the packs of leaves to conserve the packs; adding strips to the pack to form the enlargements thereof; and providing disposable apertured packs of leaves to cooperate interchangeably with retaining members that extend through the apertures of the packs to serve as enlargements for interlocking engagement with the grooves of the rotary hub.

BACKGROUND OF THE INVENTION In the construction of a flap-type abrasive wheel it is common to provide a hub structure with outer peripheral longitudinal slots that are enlarged inwardly from the periphery and to replaceably mount radial packs of abrasive leaves in the slots with enlargements on the base portions of the packs in interlocking engagement with the enlargement of the slots.

One problem to which the invention is directed is to avoid the necessity of discarding the hub structure in the event of damage in the region of the peripheral slots of such nature as to make one or more of the slots useless for its purpose of mounting a pack of abrasive leaves.

Another problem relates to the fact that the total number of abrasive leaves that may be employed on the wheel is limited to the number of leaves that can be inserted into each of the peripheral slots in the hub structure. To permit a large number of abrasive leaves to be used, each of the pack of leaves may be locally compressed in thickness to provide a restricted neck narrow enough to fit into the restricted peripheral entrance to a slot. Unfortunately such severe local compression of a pack of leaves with local stress concentration weakens the leaves to cause leaves to tear away from the pack when the pack is in operation. The problem, then, is to compact the base portions of the packs of leaves to make incurring the penalty of destructive damage to individual leaves.

Another problem to which the invention is directed it possible to use an increased number of leaves without is to provide in an economical manner efficient enlargements on the base ends of the packs of leaves as required for interlocking engagement to the packs of leaves with the peripheral slots of the hub structure. One prior art 3,548,551 Patented Dec. 22, 1970 hub structure is provided with relatively narrow longitudinal peripheral slots with the bottoms of the slots enlarged and radial blades are mounted in the slots with base portions of the blades enlarged for interlocking engagement of the slots and with a pair of packs of leaves anchored to the opposite sides of each of the radial blades. The problem in such a construction is to anchor the two packs of leaves effectively to the opposite sides of a radial blade. The outermost leaves of a pack that is on the side of a radial blade in the direction of rotation of the hub structure tend to pull free from the pack when the abrasive wheel is in operation. This problem is especially troublesome when the leaves of the packs have spaced slits that divide the leaves into parallel longitu dinal ribbon portions, some of which ribbon portions may not be effectively anchored to the radial blade.

Since the packs of leaves are eventually worn out and discarded any additions to the leaves to form the enlargements on the base ends thereof are discarded and are part of the cost of operating an abrasive wheel. Therefore a further problem to which the invention is directed is to minimize the loss that is involved in discarding the enlargements of the packs of leaves along with the abrasive leaves themselves.

SUMMARY OF THE INVENTION The problem of avoiding the necessity of discarding an abrasive wheel when one or more of the peripheral slots is too damaged to cooperate with a pack of leaves is solved by making portions of the slot structures removable for replacement. To carry out this concept, a hub with a cylindrical peripheral surface is provided with radial keyways that are enlarged inwardly of the periphery and radial key members are mounted in the keyways with portions of the key members enlarged for interlocking engagement with the keyways and with portions of the key members extending radially from the peripheral surface of the hub. The outer ends of the key members are of overhanging configuration so that each pair of successive key members cooperate with the pe riphery of the hub to form a longitudinal slot suitable for engagement with a radial pack of abrasive leaves, the slots being enlarged inwardly from their peripheral entrances to form radially inwardly facing shoulders for cooperation with enlargement on the base ends of the packs of leaves.

If any of the slots of such a hub structure becomes damaged to the extent of destroying its effectiveness for cooperation with a pack of abrasive leaves, it is a simple matter to restore the hub structure to its original state by simply substituting new key members as required. It is contemplated that the key members will be dimensioned for forced fit with the keyways to eliminate vibration between the key members and the hub but that the forced fit of a key member in a keyway will not prevent prompt removal and replacement of a key member when required.

With reference to destructive compressive damage to the abrasive leaves of a pack it has been found that the damage is due not to the degree of compression but to the concentration of the compressive forces in a narrow region to conform with the narrowed peripheral entrance to a slot in the hub structure with the pack of leaves expanding on both sides of the narrow region. It has been found that the undue damage by compression may be avoided by compressing the pack of leaves to the same degree over an extensive longitudinal portion of the pack at the base end of the pack, the longitudinal extent of the compressed area being at least equal to the depth of the hub slot into which the pack of abrasive leaves is to fit. Destructive damage has been further reduced by the additional step of introducing polymeric adhesive material into the spaces of the leaves throughout the compressed extent of the pack of leaves and keeping the base portion of the pack of leaves under sustained compression until the polymeric material cures to cement the leaves together and thus convert the extensive com pressed base portion of the pack into a solid block.

The distribution of the compression over the extensive base portion of the pack of leaves avoids undue concentration of the compressive force and the introduction of the polymeric material prior to the compression of the stack eliminates voids that may result in undesirable abrupt changes in the degree to which the pack is compressed. In addition, an important advantage of curing the polymeric material while the base portion of the pack is under compression is that damage to fibers of the leaves by compression and by penetration of abrasive particles is remedied by repair and reinforcement of the fibers by the cured polymeric material.

The block-like solidity of the finished base portion of a pack of the abrasive leaves may be understood when it is considered that the leaves are interconnected not only by the bonding material but also by the interlocking penetration of the abrasive particles at the interfaces of the leaves. Under the new concept just as many abrasive leaves are squeezed into the width of a hub slot as in the prior practice of compressing the pack in only a narrow zone but the additional leaves in a pack are provided without the usual penalty of unduly weakening the pack.

A further improvement in the preferred practice of the invention is provided in rounding the edges of a pair of jaws that is employed to compress the base portion of a pack of abrasive leaves thus avoiding the damaging effect of sharp edges and further providing a desirable transition zone from the fully compressed portion of the stack to the uncompressed portion.

Fortuitously, the solution to the problem of providing effective enlargements at the base ends of the packs of leaves in an economical manner is facilitated by the foregoing concept of converting an extensive base portion of each pack into a solid block of a length at least equal to the depth of a hub slot into which the pack of leaves is to be mounted. It has been found that the base end of such a pack of leaves may be enlarged simply by attaching an enlargement member to at least one face of the solidified base portion. The enlargement member must, of course, be effectively secured to the solidified base portion of the pack of leaves and it has been found that this purpose may be served by extending anchoring filaments through the solidified base portion of the pack and the associated enlargement member or members. The anchoring filaments, for example, may be stitches or may be staples.

An additional function of such an anchoring enlargement is to protect the outermost leaves of the base portion of the stack to keep the outermost leaves from peeling away under the stresses of normal operation of an abrasive wheel. In this regard, a feature of one parctice of the invention is that one side of the hub slot lies flat against one side of the pack of leaves throughout the depth of the slot. It is not necessary to provide a protective enlargement member on that side of the base portion because the desired protection is provided by the snugly fitting side wall of the slot. Thus in this particular variation of the invention only one side wall of the slot is undercut to form an inwardly facing shoulder for engagement by an enlargement member of a pack of abrasive leaves.

The problem of minimizing the waste of discarding enlargement members along with worn out packs of abrasive leaves is solved by employing enlargement members that may be used interchangeably with packs of leaves. Thus instead of discarding an enlargement that is employed with a disposable pack of abrasive leaves, an enlargement member is simply transferred from the worn pack of leaves to a new pack of leaves. It is c ntemplated that the interchangeable enlargement members will be of rugged construction for long service lives so that the cost of such an enlargement member is distributed over a large number of abrasive packs to reduce the cost per pack to insignificance. Thus the cost of a replacement pack of leaves does not include the cost of an associated enlargement member.

Preferably this concept of employing interchangeable enlargement members is carried out by simply providing apertures in a pack of leaves distributed across the width of the solidified base portion of the pack and by providing an enlargement member that is formed with prongs that extend through the apertures of the pack. The body of the enlargement member engages an inwardly facing shoulder on one side of the hub slot and the prongs of the enlargement body that extend through the apertures of the pack make engagement with a second inwardly facing shoulder on the other side of the hub slot.

In an abrasive wheel assembly wherein removable radial blades project from the periphery of a hub structure and two packs of leaves are anchored to the opposite sides respectively of each blade, the problem of effectively anchoring the two packs of leaves to the blade is solved in large part by solidifying an extensive base portion of each pack in the manner heretofore described and is solved in further part by placing retaining strips on the outer faces of the base portions of the two packs with anchoring filaments extending through the two opposite retaining strips, through the two packs and through the intermediate radial blade.

It has been found that in such a'construction the outermost leaves of the pack on the side of the blade in the direction of rotation of the abrasive wheel are subjected to forces that tend to tear the leaves away from the pack. This tendency has been effectively met by employing a metal retaining member on the leading pack of the pair of packs, it being satisfactory to employ a nonmetallic retaining member on the trailing pack.

The features and advantages of the invention may be understood from the following detailed description and the accompanying drawings:

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings which are to be regarded as merely illustrative:

FIG. 1 is a side elevational view partly in section of a flap-type abrasive wheel in which the peripheral slots for anchoring the radial packs of abrasive leaves are formed by removable radial key members;

FIG. 2 is a more or less diagrammatic perspective view showing an operation whereby an extensive base portion of a pack of leaves may be impregnated within polymeric adhesive material in preparation for converting the base portion into a solid block;

FIG. 3 is a diagrammatic sectional view showing how a pair of jaws with rounded edges may be employed to compress an extensive face portion of a stack of abrasive leaves and to maintain the extensive base portion under sustained compression until the incorporated polymeric material cures to solidify the base portion;

FIG. 4 is an elevational view of a pack of abrasive leaves with an extensive solidified base portion and with two enlargement members attached to the pack by stitching that extends through the pack and the two enlargement members;

FIG. 5 is a similar view showing how staples may be employed instead of stitching for connecting the two enlargements to the solidified base portion of the pack;

FIG. 6 is a fragmentary sectional view of a hub of an abrasive wheel wherein the hub is formed with slots for interlocking engagement with packs of abrasive leaves with only one enlargement member required for each hub slot because one face of the hub slot conforms snugly to the base portion of the pack;

FIG. 7 is a sectional view similar to FIG. 3 showing how a pair of jaws with rounded edges may be employed to compress the base end of the stack of leaves after the base end is impregnated with the polymeric material;

FIG. 8 shows how a single tapered enlargement may be attached to one side of the solidified base portion of the pack of leaves by stitching that extends through the enlargement member and the solidified base portion;

FIG. 9 is a view similar to FIG. 8 showing how staples may be substituted for stitching;

FIG. 10 is a fragmentary sectional view similar to FIG. 6 showing how both of the side Walls of the hub slots may be overhanging configuration to cooperate with corresponding tapered enlargement members on the base portions of packs of leaves;

FIG. 11 is a view similar to FIG. 8 showing how stitching may be employed to attach tapered enlargement members to the opposite sides of a solidified base portion of a pack of leaves;

FIG. 12 is a view similar to FIG. 9 showing how staples may be employed to attach the pair of tapered enlargement members to the base portion of the pack of leaves;

FIG. 13 is a fragmentary sectional view showing how an interchangeable enlargement member may cooperate with the solidified base portion of a pack of leaves to anchor the pack of leaves in a peripheral slot of a hub structure;

FIG. 14 is a perspective view of the pack of leaves shown in FIG. 13 together with the enlargement member that is used interchangeably with such packs of leaves;

FIG. 15 is a fragmentary sectional view of an abrasive wheel in which two packs of abrasive leaves are anchored to the opposite sides respectively of each of a circumferential series of removable blades that extend radially from the periphery of the hub, the pair of packs associated with each radial blade being anchored by filements that extend through the packs and through the radial blade and additionally extend through retainer strips on the outer faces of the base portions of the two packs; and

FIG. 16 is an elevational view of one face of the abrasive leaf assembly shown in FIG. 15, the view indicating how the leaves of the pack may be divided by short slits into ribbon-like portions with the ribbon-like portions secured by the corresponding retaining members at the base ends of the two packs of leaves.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an abrasive wheel for mounting on a power driven shaft, the abrasive wheel having a hub structure 20 with a peripheral or outer circumferential surface 22 and with a series of circumferentially spaced longitudinal keyways 24 that open onto the peripheral surface. Each of the keyways 24 is formed with an enlargement 25 and a corresponding key member 26 is mounted in each keyway with a forced fit, the key member having an enlargement 28 for interlocking engagement with the enlargement 25 of the keyway. Each of the key members 26 is of tapered configuration as shown and each has a pair of opposite longitudinal flanges 32 that form radially inwardly facing shoulders 34. Thus each pair of the successive key members 26 cooperates with the peripheral surface 22 of the hub structure to form a longitudinal slot wherein a radial pack 35 of abrasive leaves 36 may be mounted in radially projecting position. The radial leaves may be made of suitable flexible sheet material such as cloth with particles of abrasive material bonded to at least one face of each sheet.

Each of the packs 35 is adapted for releasable interlocking engagement with a longitudinal slot that is formed by a pair of the key members 36. In the construction shown the inner or base end of each pack 35 is enlarged by the addition of a pair of strips or enlargement members 38 on the opposite faces respectively of the pack. The strips or enlargement members 38 may be made, for example, of fiberboard or a suitable vinyl plastic. The preferred construction for the radial packs 35 may be understood from the following description of the preferred method of fabrication.

A troublesome problem in the construction of an abrasive wheel of the general type shown in FIG. 1 is that spaces necessarily exist between the peripheral slots in which the packs of leaves are mounted so that substantially less than the whole circumference of the hub structure is available for the abrasive leaves. The problem is to minimize the extent to which the total number of abrasive leaves must be reduced to provide circumferential spaces between the longitudinal peripheral slots.

As heretofore stated, one solution to this problem has been to provide an oversized pack and to compress the oversized pack locally to form a neck in the pack of sufficiently reduced thickness to fit into the restricted peripheral entrance of the slot. As heretofore mentioned, the concentration of compressive stress required to form a restricted neck in a pack of leaves results in structural damage to the individual abrasive leaves and a shortened service life for the pack.

The fabrication process taught by the present invention also starts with an excess number of leaves to make a pack of abrasive leaves that is oversized relative to the width of the peripheral entrances to the longitudinal slots of the hub 20. A base portion of the oversized pack of leaves is saturated with a suitable polymeric material such as an epoxy resin, the length of the base portion being at least as long as the depth of the peripheral grooves of the hub. For this purpose, the base end of the pack of leaves may be dipped in a low viscosity epoxy resin or with the pack of abrasive leaves held between the fingers, the low viscosity epoxy resin may be applied to the edges of the leaves of the base portion of the pack by a nozzle 40 of a suitable applicator or dispenser. With the base portion of the pack of leaves well permeated with the fluent bonding material, the base portion of the oversized pack is placed between a pair of jaws 42 which are at least as wide as the depth of the peripheral grooves of the hub structure and the two jaws are hydraulically actuated to subject the base portion of the oversized pack to high magnitude pressure. The compressive pressure, appreciabaly reduces the thickness of the base portion of the oversized pack with consequent increase in the local density and with consequent interlocking of the leaves of the pack by the penetration of abrasive particles of leaves into the sheet material of ad acent leaves.

The oversized pack of leaves is kept under pressure by the pair of jaws 42 until the epoxy resin cures to transform the base portion of the pack into a solid block. The number of leaves selected for the oversized pack and the degree of compression by the paid of jaws 42 are such that the thickness of the solidified block at the base end of the pack is precisely the thickness to fit snugly in the narrowed peripheral entrance to a longitudinal peripheral slot of the hub structure 20.

In the preferred practice of the invention the two jaws 42 are formed with rounded edges 44 to avoid an abrupt boundary to the compression zone that might result in local damage, especially damage to the outermost leaves of the pack. The rounded edges 44 result in a desirable transition to the compression zone without sharp bending of the outermost leaves.

The next step is to attach the two enlargement members 38 etfectively to the opposite faces of the solidified base portion of the oversized pack of abrasive leaves. FIG. 4 shows how the two enlargement members 38 on opposite sides of the pack may be secured by extending fastening filaments in the form of stitches 45 through the base portion of the pack and through the two enlargement members. FIG. 5 shows how the fastening filaments that 7 extend through the base end of the pack and the two enlargement members 38 may be in the form of staples 46. It is important to note that the stitches or staples do not engage the outer leaves of the base portion of the pack and therefore do not damage the outer leaves by damaging local concentration of stress.

In FIG. 6 illustrating a second practice of the invention a hub structure is formed with a series of circumferentially spaced longitudinal slots each of which has a bottom surface 52, an approximately radial side wall 54 and an opposite side wall 55 that is inclined from a radial direction to overhang the bottom surface of the slot, the two side walls cooperating to form a restricted peripheral entrance to the slot.

A pack 56 of abrasive leaves is mounted in each of the longitudinal peripheral slots of the hub 50 with one face of the base portion of the pack fitting snugly against the radial side wall 54 of the slot and with the opposite face of the base portion of the pack provided with a tapered or wedge-shaped strip or enlargement member 58 in interlocking engagement with the overhanging side wall 55. Thus the overhanging side wall 55 forms a tapered inwardly facing retaining shoulder and the wedge-shaped enlargement member 58 engages this retaining shoulder to anchor the base end of the pack in the slot. The fact that one face of the base end of the pack is held firmly against the radial side wall 54 of the slot provides adequate protection and anchorage for that face of the base end.

Each of the packs 56 of abrasive leaves may be fabricated in the general manner heretofore described. Thus FIG. 7 shows a pair of jaws 60 with rounded edges 62 compressing a base portion of the pack that is saturated with epoxy resin, the base portion of the pack being at least as long as the depth of the longitudinal peripheral slots of the hub structure 50. FIG. 8 shows how a tapered enlargement member 58 may be attached to the solidified base portion of the pack 56 by stitching 64 and FIG. 9 shows how staples 65 may be employed for the same purpose.

FIG. 10 illustrates a third practice of the invention in which a hub structure is provided with longitudinal peripheral slots to receive the base portion of corresponding packs 71 of radially extending abrasive leaves. Each of the longitudinal peripheral slots has a bottom surface 72 and two side walls 74 that are inclined to overhang the bottom surface and thus form a restricted peripheral entrance to the slot. The inclined opposite side walls 74 of the slot form what may be termed tapered inwardly facing retaining shoulders and the solidified base portion of the corresponding pack 71 is provided with a pair of tapered enlargement members 75 for interlocking engagement with the tapered retaining shoulders.

Each of the packs 71 of abrasive leaves shown in FIG. 10 may be constructed in the general manner heretofore described. Thus FIG. 11 shows how the two opposite enlargement members 75 may be secured to the solidified base portion of a pack 71 by means of switching 76 and FIG. 12 shows how staples 78 may be employed for the same purpose.

FIGS. 13 and 14 show how an interchangeable anchorage member 102 may be employed with a pack 104 of abrasive leaves to avoid the expense of providing the pack with permanent enlargement means for interlocking engagement with a longitudinal peripheral slot of the hub structure. The pack 104 is fabricated in the general manner heretofore described, the pack having a solidified base portion 105 of a dimension longitudinally of the pack at least equal to the depth of the hub slot in which the pack is to be mounted. The base portion 105 is not only solidified but is also compressed as heretofore described to increase the number of leaves that may be placed in the hub slot.

It is contemplated that the solidified base portion 105 of the pack 104 will be apertured to provide shoulder member 102. In the construction shown the base portion 105 of the pack is provided with a plurality of apertures or bores 106 which are distributed across the width of the base portion of the pack and each of which provides a surface or shoulder means for retaining engagement by the cooperating anchorage member.

In this instance, the anchorage member 102 is a sheet metal stamping having a body portion 108 with a plurality of bent prongs 110 extending therefrom for insertion into and through the corresponding apertures 106.

FIG. 13 indicates the manner in which a pack 104 is mounted in a longitudinal peripheral slot of a hub structure. The longitudinal slot in which the pack is mounted has a bottom wall 112 and two opposite overhanging side walls 114 which form a pair of inwardly facing longitudinally retaining shoulders 115. It can be seen in FIG. 13 how the body portion 108 of the anchorage member 102 makes interlocking abutment with one of the two retaining shoulders 115 with the prongs 110 of the anchorage body extending through the apertured pack into engagement with the second retaining shoulder 115.

It is apparent that since it is not necessary to provide each pack 104 with an enlargement for interlocking engagement with a hub slot, the pack is highly economical to produce. It is further apparent that an anchorage member 102 is of rugged construction so that the cost of the anchorage member may be distributed over an indefinite number of the disposable packs 1004.

FIGS. 15 and 16 illustrate another practice of the invention in which a hub structure 80 is provided with a circumferential series of removable radial key members 82, each of which carries a pair of packs 84 of abrasive leaves. The hub structure 80 is provided with radial peripheral keyways 85 to receive the radial key members 82, each of the keyways being inwardly enlarged as indicated at 86 and each of the radial key members having a corresponding inner enlargement 88 for interlocking engagement with the keyway. The radial k y members 82 which may be extruded aluminum members fit in the radial keyways 85 in a snug but removable manner to permit the pairs of packs 84 to be readily replaced when they become worn out. The two packs 84 of each of the pairs of packs are suitably attached to the opposite faces of the corresponding radial key members 82 with the base ends of the packs in abutment with the peripheral surface 90 of the hub structure 80. It is contemplated that the base portion of the packs 84 will be compressed and solidified in the manner heretofore described and it is further contemplated that protective strips 92 and 94 will be attached to the outer faces of the base portions of the two packs respectively with the two packs attached to the radial intervening key member by fastening filaments 95 which pass through the two strips 92 and 94 as well as through the two packs 84 and through the intervening radial key member 82.

As indicated by the arrow 96 in FIG. 15, it is contemplated that the hub structure 80 will rotate counterclockwise with the consequence that the left pack 84 of each pair of packs will be the leading pack and the right pack will be the trailing pack. The leading pack of the pair is sharply flexed by a workpiece in an abrasive operation and intermittently makes contact against the workpiece with the consequential tendency for the outer leaves of the leading pack to be pulled away from anchorage to the pack. In this regard a feature of this practice of the invention is that the strip 92 on the leading pack 84, i.e., the strip on the side of the key member that is in the direction of rotation, is made of a suitable metal such as steel to withstand the higher stresses on the leading side of the pair of packs. The other strip 94 may be made of less expensive material such as a vinyl plastic.

As shown in FIG. 16, the individual leaves of a pack 84 may have multiple short slits 98 lying longitudinally of the leaf to divide the leaf into longitudinal ribbon portions 100. It has been found that the described construction with the two strips 92 and 94 anchored by stitching or other fastening filaments that extend through the corresponding radial blade 82, each of the ribbon portions 100 of the leaves of the pack will be effectively secured against forces that tend to pull the ribbon portions free.

Here again the provision of the two strips on opposite faces of the basic portion of the pack keeps the stitches or staples from making damaging pressure contact with the outer leaves of the base portion. In the absence of the two strips the stitches or staples would locally depress the outer leaves with undue stress concentration.

My description in specific detail of the selected embodiments of the invention will suggest various changes, substitutions and other departures from my disclosure within the spirit and scope of the appended claims.

What is claimed is:

1. In an abrasive drum, having a series of packs of flexible abrasive sheets mounted longitudinally on an axial hub, said hub being provided with longitudinal slots circumferentially spaced around the cylindrical surface of said hub, each of said slots having an inwardly enlarged transverse cross section, each of said packs being replaceably mounted to said hub by the reception of the base of said pack in a corresponding one of said slots, an improved construction for said pack comprises:

each of said packs being an assembly of abrasive sheets extending longitudinally of a corresponding one of said slots, said sheets having outer wearing edges freely opening from one another, and inner base portions received into said slot;

a solid block formed from the base portions of said abrasive sheets and impregnated plastic material, compressed to a uniform compactness, said block seating on the bottom of said corresponding slot, said block having a longitudinal extent the length of said pack, a radial extent relative to said hub not less than the depth of said slot, and dimension transverse to said slot substantially the same as the opening of said slot; and

a protective enlargement member integrally attached to at least one longitudinal face of said solid block, said enlargement member extending longitudinally the length of said pack, and extending radially at least to the opening of said slot, said protective enlargement member being interposed between said block and the adjacent sidewall of said slot, and having an outer face inwardly enlarged from said block to mate closely with the adjacent wall of said slot, and provide anchoring of said pack in said slot.

2. In an abrasive drum, having a series of packs of flexible abrasive sheets mounted longitudinally on an axial hub, said hub being provided with longitudinal slots circumferentially spaced around the cylindrical surface of said hub, each of said slots having inwardly diverging sidewalls, each of said packs being replaceably mounted to said hub by the reception of the base of said pack in a 10 corresponding one of said slots, an improved construction for said packs which comprises:

each of said packs being an assembly of abrasive sheets extending longitudinally of a corresponding one of said slots, said sheets having outer wearing edges freely opening from one another, and inner base portions received into said slot;

a solid block formed from the base portions of said abrasive sheets and impregnated plastic material, compressed to a uniform compactness, said block seating on the bottom of said corresponding slot, said block having a longitudinal extent the length of said pack, a radial extent relative to said hub not less than the depth of said slot, and a dimension transverse to said slot substantially the same as the opening of said slot; and

a protective wedge member integrally attached to at least one longitudinal face of said solid block, said wedge member extending longitudinally the length of said pack, and extending radially at least to the opening of said slot, said wedge member being interposed between the lateral surface of said block and the adjacent sidewall of said slot, and having an outer face inwardly diverging from said block to mate closely with the adjacent wall of said slot, and provide anchoring of said pack in said slot.

3. An abrasive pack as described in claim 2 in which said wedge member and the base portion of said sheets are bonded together by a plastic resin to form a unitary rigid structure.

4. An abrasive pack as described in claim 2 in which said wedge member is integrally attached to said block by filaments passing tranversely through said wedge member and said block.

5. An abrasive pack as described in claim 2 in which both faces of the base of said pack are shielded from the adjacent walls of said slot by wedge members having outer faces diverging to mate closely with the diverging walls of said slot.

6. An abrasive pack as described in claim 2 in which said wedge member is integrally attached to said block by staples passing tarnsversely through said wedge member and said block.

7. An abrasive pack as described in claim 2 in which said wedge member is comprised, at least in part, of plastic material, and said wedge member and said block are bonded into a unitary, plastic impregnated structure.

References Cited UNITED STATES PATENTS 2,259,475 10/1941 Koether 51-337 2,599,961 6/1952 White 51-337 2,804,730 9/ 1957 Block 51337 2,821,819 2/ 1958 Bernstein et a1 5 l337 2,871,632 2/1959 Cosmos 51-337 3,053,021 9/1962 Block 51337 3,141,269 7/1964 Block 51-337 3,212,219 10/ 1965 Gillett 51-337 LESTER M. SWINGLE, Primary Examiner 

